This is really a question for Microsoft. You should contact their forum for support. Microsoft did push Windows 10 on you, and every thing worked until you went to 1709.

And, your processor (1st generation) is very old (8 years old). And, it is correct that your processor is not supported on Windows 10.

However, I have seen this on several PCs.

Unplug all devices that are not necessary - printers, scanners, external drives, etc. and even devices you may have connected on internal motherboard headers, dvd/cd drives, and I mean everything.

Keep only what you absolutely need, like the mouse and keyboard, and LAN connection. Do not use or attach any hubs.

Do the update to 1709. It will likely work. If so, then begin by re-connecting all of the devices you have removed, one by one, until you find the offending device. I will likely still work, but at least you will know for the next time.

If this did not work, you can thank Microsoft as they are the ones who are not properly recognizing drivers/devices that they did on 1607 when upgrading to 1709.

If you have a laptop that has the same update issue from 1607 to 1709, you most likely cannot do anything. For example, an internal ricoh sd card reader driver will work on 1607, but not 1709. Microsoft knows this, but will not correct the problem. And, taking the laptop apart to unplug the device is not practical or possible.

Now, my personal opinion - get a new or newer system and avoid the problems Microsoft has imposed on you and older hardware.

Yes, the processor is "old". But in comparison with current processors it is not the slowest (12 cores), so it was a bit more expensive at that time. So far there has been no reason for an exchange.

Windows 10 has been running on the computer for a long time. There were no issues with the compatibility test at that time. This means that the processor was never excluded from using Windows 10. Where does this information come from?

Are there new restrictions for follow-up updates/builds/versions?

If this is the case, then a compatibility check (analogous to the first release of Win10) is always required before such an update. It must inform the user which devices are not compatible and why.

The suggested solution to "disassemble" the computer is reasonable, but not acceptable/practical.

A pure driver detection problem is of course not a great Microsoft performance and is not acceptable. Nevertheless, it should be possible to get the latest driver from the manufacturer and update it manually in Win 10.

Exactly that leads to my next problem. The Intel® Driver and Support Wizard does not work. Also from Intel the user does not get a qualified error message. In the meantime, I have noticed that there are separate discussions on this subject.

(At the end, it's no problem if the system has to stay on a particular build, as long as all security relevant updates are still delivered for this build)

The official answer is that your processor is not supported on Windows 10. However, there are older processors that are working with 1709.

I do not believe it is an issue with your (unsupported) processor. Like I said, just unplug every thing that you do not need, especially any usb devices/hubs, and try again.

The Intel driver and support assistant is intended for INTEL boards.

Regarding getting the current driver from the manufacturer, sounds good. But, which driver do you need? In my example, the ricoh sd driver is the latest available and works on 1607 but not 1709. Ricoh has long since dropped support for this specific reader. Getting a current driver from the manufacturer is simply not possible.

As far as being on a particular build, W10 will try again, and again, and again to get you on 1709. I purposely had to move a machine back to W7 just to avoid the constant reboot, download, reboot loop.

No one is asking you to disassemble your machine. Until you know what the offending device is, you can try what I proposed. Maybe just start with the external devices and hubs, and keep only a wired keyboard and mouse. On my own personal desktop, the offending device was the USB hub in a dell monitor. Once unplugged, the upgrade to 1709 succeeded.

So, either try and determine what is causing the problem, or get a new system. I know it is not the ideal answer, but there are many users out there experiencing the same 1607 to 1709 problem. Remember, Microsoft can decide at any time to completely drop support for "old", unsupported hardware.